Lithium Extraction from Brine Using Membrane-based Bipolar Electrodialysis

As the demand for lithium batteries increases, the search for more efficient means of lithium extraction from brine sources has accelerated. However, these brines are complex and contain contaminants such as magnesium, calcium, and sodium, with divalent ions being difficult to remove via conventional ion sorption processes. Selective ion-exchange processes have been developed for upgrading such brines, but these methods typically produce a chloride salt product which is subsequently precipitated as lithium carbonate or electrochemically converted to the more-desirable LiOH in a separate process. Direct one- or few-step upgrading of Li-containing brine to LiOH is desired to avoid unnecessary processing of LiCl. Direct LiOH production from brine mixtures via bipolar membrane electrodialysis (BPED) is being considered. However, most commercial cation exchange membranes (CEMs) used in BPED systems do not possess sufficient monovalent/divalent ion selectivity to prevent precipitation of poorly soluble calcium and magnesium hydroxides in the base product of BPED systems, which foul and damage membranes. Thus, current CEMs are limited to applications where the feed concentration of divalent cations is below 10 ppm. Here, we report synthesis and characterization of Li-selective CEMs for BPED. This process potentially enables the upgrading/conversion of lithium to be practiced on less-processed brines with higher monovalent and divalent ion contamination.